The present invention relates to a tonometric measuring head for bringing an analyzable measuring medium to a composition consistent with an individual to be examined and non-invasively through the outermost tissue layer, said measuring head comprising: a substantially sealed chamber, having a wall whose oppositely facing sides are essentially made of pliable membrane materials, at least one of said materials comprising a pliable, first membrane material permeable to a gas to be analyzed but impermeable at least to solids and liquids; a measuring medium in a cavity within the chamber wall; at least one guide means extending between said chamber and an external device, said guide means and the chamber wall being tightly linked to each other. In addition, the invention relates to a method during parturition for monitoring non-invasively the prenatal and natal physical condition of a child, said method comprising the steps of: introducing an elongated and flat measuring instrument, provided with an active side and an inactive side, between a birth canal and a child; setting the measuring instrument, during said introduction, with its active side towards the child and its inactive side towards a wall of the birth canal; positioning the measuring instrument in such a way that its length reaches the area of a cervix uteri.
This type of sampling means have been described in publications U.S. Pat. No. 4,643,192, U.S. Pat. No. 5,526,809 and U.S. Pat. No. 5,479,923. All these publications disclose tonometric measuring heads provided with one or more spherical chambers, having walls which are permeable to a gas to be examined. In these publications, the gas to be analyzed is carbon dioxide and, furthermore, the first two publications necessitate the measurement of a bicarbonate concentration. According to the cited publications, such a tonometric sampling means is introduced into a lumen of the body of a patient to be examined, such as the stomach or intestines, whereby a gas to be examined diffuses from the patient through a wall of the tonometric sampling means into a liquid contained in the chamber. Thereafter, the liquid present within the sampling chamber is examined for its composition either by delivering it to a laboratory, which is the case in the first two publications, or by circulating it along one or two tubes extending between the sampling means and an external analyzer to detectors included in this analyzer. It is typical of all these tonometric measuring heads to follow the above-described principle in terms of introducing the same within a body cavity of the patient for a measuring procedure.
Monitoring a physical condition, such as the oxygen supply, of a presently delivered baby is known to be very difficult, as it is inconvenient to attach any measuring sensors to a prenatal or natal child. At the moment, a presently delivered child can be monitored either in a very old-fashioned manner by listening to heart sounds through the abdominal layers of a parturient or alternatively by an EKG-electrode screwed on the head of a baby for obtaining the heart rate, which roughly represents the baby""s oxygen supply. These are quite inaccurate and unreliable methods. The publications EP-0,135,840, EP-0,575,737 and EP-0,509,310 only disclose pulse oximeter sensors, intended for monitoring the condition of a presently delivered baby by placing the same alongside the baby""s head and by using infrared absorption for directly measuring the blood oxygenation degree of the baby. Hence, these sensors include a radiation source and a detector, such that the radiation travels through the tissue of a baby""s head. However, the pulse oximetry measurement relates to a device and a method highly sensitive to artifacts. Thus, the working conditions for pulse oximetry during parturition are highly unfavourable due to movements of both the baby and the parturient. Therefore, the genuine applicability of a pulse oximeter device in childbirth is highly questionable. The cited publications do not deal with this problem at all, but primarily these cited publications describe means for immobilizing this sensor assembly and for holding it against the head of a presently delivered baby. The publication EP-0,135,840 discloses both a simple flat-shaped sensor, hopefully holding on to a measuring site without special procedures, and a suction-pad resembling sensor attached to a child by the application of vacuum. The publication EP-0,575,737 discloses an elongated sensor, intended to be held at a measuring site by means of a folded spring element made of steel. In the publication EP-0,509,310, on the other hand, the intention is to hold an elongated sensor at a measuring site by means of an inflatable cushion in its extreme end, the purpose of said cushion, in its capacity as a thickening, being to prevent the sensor from slipping off from between the presently delivered child and the birth canal.
The publications EP-0,440,741 and WO-91/07910 describe sensors comprising both a pulse oximeter sensor and an EKG-sensor. The only means for the attachment of a sensor described in the publication EP-0,440,741 is a vacuum-operated suction pad assembly, while the publication WO-91/07910 discloses an inflatable cushion mounted on the extreme end of an elongated sensor, intended for preventing the sensor from slipping off from its position between the presently delivered baby and the birth canal.
On the other hand, the publication U.S. Pat. No. 4,197,853 describes a measuring sensor for measuring the partial pressures of oxygen and carbon dioxide through the skin of a patient, i.e. transcutaneously. The sensor of this publication includes in itself all detecting elements, in this case electrochemical cells. Such a transcutaneous measuring sensor is quite bulky and, as such, only applicable to the examination of a patient from outside the body, but it is not suitable for measuring the physical condition of e.g. a fetus or a presently delivered baby. As for this application, the sensor described in the cited publication is an element far too bulky and hard. Neither does the publication describe any means for its attachment to a measuring site or otherwise immobilizing it at a measuring site. Applying a measurement to an unrestrained and thus totally accessible patient by a transcutaneous procedure does not require any attachment means as the sensor can be simply pressed manually against the skin. Such application of a measurement to a fetus and a presently delivered baby is not possible.
An object of the invention is to provide a measuring instrument that could be used for measuring or monitoring, for example, the physical condition of a presently delivered child. A particular object is to monitor the sufficiency of oxygen supply for a baby during parturition. A second object of the invention is such a measuring instrument which could be used for reliably measuring explicitly the condition of a presently delivered baby without the parturient affecting the measuring result through the measuring head. A third object of the invention is such a measuring instrument which provides a result affected as little as possible by movements of the presently delivered child and the mother. A fourth object of the invention is such a measuring instrument which has such a design that, under no circumstances, could it possibly be harmful either to the presently delivered child or the mother, and that it would interfere with the course of parturition as little as possible. A fifth object of the invention is such a measuring instrument which can be used for measuring the presently delivered child irrespective of the parturient and also, if necessary, the parturient irrespective of the presently delivered child. A sixth object of the invention is such a measuring instrument which, in general sense, can be used for measuring the physical condition of a single individual, such as a human being or an animal, irrespective of another individual, such as a human being or an animal, while these two individuals are in contact with each other. In particular, the meaning of this is that it must be possible to perform measurements over those sites or areas, at which the individuals are in contact with each other. A seventh object of the invention is such a measuring instrument which would remain as immobile as possible for example in the birth canal against the outermost cellular layer of a baby or, in the contact circumstances of other individuals, against any individual to be measured at a given time. An eighth object of the invention is such a measuring instrument which would be easy to use, easy to sterilize and to maintain sterilized. A ninth object of the invention is a measuring instrument which, if necessary, could be designed and manufactured to measure an object for single concentrations of various component media or for concentrations of a plurality of various component media.
The above drawbacks can be eliminated and the above-defined objects can be achieved by means of a measuring head of the invention, and by means of a method of the invention, which is characterized by what is set forth in the claims.
The most important benefit offered by the invention is that the inventive measuring head can be used for measuring and monitoring the physical condition of a presently delivered baby through the baby""s skin without having to attach essentially anything to the baby. A second benefit offered by the measuring head of the invention is that it remains very reliably immobilized in the birth canal between the child and a wall of the birth canal and that, nevertheless, the measuring head can be positioned by a physician or a nurse in a site appropriate in terms of the measurement and progress of parturition. A third benefit offered by the measuring head of the invention is that it can be used for reliably measuring the condition of a baby without the mother""s body, i.e. the birth canal wall, having any essential effect on the measuring result. A fourth benefit offered by the measuring head of the invention is that the device is highly insensitive to the movements of an object of measurement and, thus, despite the movements of a baby or a parturient, the measuring head is capable of producing a reliable measuring result. A fifth benefit offered by the measuring head of the invention is that various embodiments of the device can be used for measuring at least the carbon dioxide concentration and/or oxygen concentration from an object of measurement, and possibly other concentrations as well by appropriately selecting materials and/or detecting elements for the measuring head. A still further benefit of the invention is that the inventive measuring head can be used for measuring and monitoring other objects as well, such as human beings and animals in a mutual contact situation.